1. Field of the Invention
The present invention relates to a method of relaying data, and more particularly, to a method of cooperatively relaying data in cellular networks for Broadcast Multicast Services (BCMCS). Although the present invention is suitable for a wide scope of applications, it is particularly suitable for relaying data in cellular networks.
2. Discussion of the Related Art
A Broadcast Multicast Service (BCMCS) provides the ability to transmit the same information stream to multiple users simultaneously. More specifically, the BCMCS is intended to provide flexible and efficient mechanism to send common or same information to multiple users. The motivation for this service is to achieve the most efficient use of air interface and network resources when sending the same information to multiple users. The type of information transmitted can be any type of data (e.g., video, text, multimedia, streaming media). The BCMCS is delivered via the most efficient transmission technique based on the density of the BCMCS users, information (media type) being transmitted, and available wireless resources.
Transmission territory for each BCMCS program can be independently defined. Here, the BCMCS program refers to a logical content transmitted using the BCMCS capabilities. Moreover, the BCMCS program is composed of one or more internet protocol flows. In operation, the programs can be transmitted in time sequence on a given channel. The BCMCS programs can be transmitted to all or selected regions of the network. These regions constitute the transmission territory which refers to an area of wireless network coverage where transmission of a BCMCS program can occur. The transmission territory can be defined by a set of cells/sectors that can transmit a BCMCS program. In addition, the BCMCS programs can be received by all users or can be restricted to a subset of users via encryption.
In the BCMCS, retransmission and acknowledgement are not required since the type of transmission is “one way” and/or “one to many.”
The BCMCS subscription is normally associated with the program (e.g., ABC, TNT, ESPN), not the content (media type such as music, video, etc.). That is, by selecting the program, the user selects the type of content the user wishes to receive.
The BCMCS in cellular networks typically incur coverage holes and limited capacity (channels) per carrier. This can arise due to channel propagation impairments (e.g., severe shadowing), large cell sizes (e.g., with site-to-site distances greater than 2 km) due to base terminal station (BTS) deployments, limited bandwidth, and interference from adjacent cells transmitting different BCMCS content. Consequently, BCMCS coverage becomes limited along with broadcast multicast system capacity.